It is possible to measure distances between two locations with the use of electromagnetic signals. Devices which do such measuring are known in the art as "range finders." An electromagnetic transmit signal may be sent from a first location to a second, and an electromagnetic return signal may be immediately sent back. The time between the sending of the transmit signal and the receiving of the return signal (the "two way time of flight") may be measured. The two way time of f light may then be correlated to the distance between the two points. The distance can be calculated by multiplying the known velocity at which the electromagnetic signal travels by the two way time of flight.
A parameter which greatly affects the range and sensitivity of a distance measuring system is the amount of return signal which can be collected and utilized at the point of origin. The larger the collected signal, the greater the distance can be between the two locations while still making an accurate two way time of flight measurement. Thus, it is desirable to make use of as large a portion as possible of the return signal when measuring two way time of flight.
Additionally, in certain applications, it is desirable to measure distance between a second location and a first location where the first location lies in any arbitrary radial direction from the second. Under such circumstances, the apparatus at the second location must be capable of returning a signal to the first location no matter where the first location lies.
Accordingly, among other things, the present invention provides f or extremely efficient collection of the return signal used for measuring two way time of flight, thus greatly enhancing range and sensitivity of the range finding system. Such efficiency also permits the range finder to be small and portable, so that it is suitable for use in golfing.